Picture-projecting apparatus



Jan. 22, 1929.

P. E. CHAPMAN PICTURE PROJECTING APPARATUS Origin a1 Filed July 26, 19132 Sheets-Sheet V 2: 2? Y M W @Z;

Jan. 22, 1929.

1,699,833 P. E. CHAPMAN PICTURE PROJECTING APPARATUS Original Filed July26, 1915 2 heets-Sheet 2 wr/gssEs I Patented Jm. 22, 1929.

* UNI-Tao STATESI'PATENT OFFICE.

P111303! 3. W, '0! S1. LOUIS, MISSOURI, ASSIGNOR T WALTER- A. HOBNBB, OFCHICAGO, mom

rIcrUna-rnomc'rmo arrm'rua Substitute for application Serial Io.781,426, filed July 26, 1813. Thii application filed December 4, 1918. I

Serial 110. 848,449.

The object of my invention is for projecting what iscommonly known asmovmg pictures, the object being to avoid the flicker of the picture onthe screen. Projecting machines, as at present operated, expose apicture to view on the screen for a brief space of Figure 1 is aconventional illustration of my improved projecting machine.

Figure 2 is a diagrammatic illustration of one form of my invention.

Fig. 3 is a diagrammatic illustration of the prisms used in connectionwith my invention. Figure 4 is a similar view showing said prisms curvededgewise.

Figure 5 is a diagrammatic view of a modified form illustrating mirrorsas deflecting surfaces.

Figure 6 is a diagrammatic view illustrating the oppositely movingprism.

In the drawings I have conventionally illustrated several parts enteringinto my invention and for the purpose of clearness have omitted anenclosing housin supports for shafts, etc., but it'is understoo thatthese and other accessories, necessary to successfully practice myinvention, should all be present.

1 indicates a shaft which is rotated from some suitable source of power,said shaft driving a worm 2 meshing with a worm-gear 3 conjoined to adelivery sprocket 4 over which the film 5 passes on its way to a take-upreel 6. 1

9 indicates a feeding cam in the form of a spiral having its endsoverlapping and which cam operates with the pins or projections ofsprocket 7 which is connected with a feed sprocket 8.

The film 5 passes an opening commonly called the aperture, in a. plate10, which opening or aperture is of such size as to accommodate one ormore pictures at the same time. In the mechanism illustrated in theaccompanying drawings, the aperture is of the size to accommodate twopictures. The film is fed from the primary reel over a feed sprocket 111 power of the prism at the time that the picshown a prism of varyingpower, it will be which latter is driven by means of a worm gear 12.Shaft 13 is geared to shaft 1- by means of suitable gearing. I haveshown the connecting train to consist of three gear wheels 14, 15 and16, the first being mounted on shaft 13 and the last on shaft 1, and towhich gears are conjoined rollers 17, the ratios of\ whose diameters areequal to the ratios of the pitch diameters on said gears. The pur- 'poseof this is to enable the gears to run smoothly and noiselessly and toestablish as far as practicable a perfect synchronism and fixed phaserelation in the rotation of the shafts 1 and 13. It is obvious thatthere are other ways of securing synchronism and fixed phase relation inthe rotation of these shafts.

In order to full understand the action of prisms in refractin orreflecting rays of light, as I propose utilizing reflection or prismaticdeflection, I will refer to Figure 2 in which a indicates a source oflight,

6 the usual condensing lenses,

0 the picture to be projected,

d the deflecting prlsm,

e the'objective lens or system of lenses,

fthe image thrown on the screen.

By examination of this figure, it will be seen that the rays of lightare condensed onto the prism d, are there deflected and after passingthrough the objective lens or system of lenses, the picture isreproduced, enlarged (and inverted) on the screen.

From an examination of the dia ram shown in Figure 2 it will be observedt at a change in the power of the prism d would cause a change in theposition of the picture on the screen 7. This is the fundamentalprinciple of my present invention and a fact of 'which I take advantageby changing the ture c is moving, to maintain the image on the screenstationary so that I am thus enabled to dispense with the use of adarkening shutter.

Referring now to Figure 3 in which I have observed that at the righthand end al where the faces of the prism are almost parallel to eachother, said prism is of relatively lower power, while at the other end(1 the angularity between the faces of the prism has been increased andthe prism at this end may be said to be of high power, it is therefore aprism of varied strength. If such a prism were arranged to slidelongitudinally between the picture and objective lens, assum-.

ing for the moment that the piqture was sta-. tionary, it is obviousthat the image on the screen would be raised or lowered by the varyingdeflecting powers of the said prism. So likewise will it'be noted thatif, at the timeof moving the prism, the'picture c was llkewlse moved,the speed of movement being proportionate to the speed of movement andthe deflective powers of the prism, the image on the screen could bemaintained stationary.

The changing angularitv of theprism wlth respect to the picture wouldhave a tendency to deflect opposite edges of the picture .unequally,with the result that the picture would be askew on the screen. It is,therefore, necdone by means of a correcting prism d which is arranged-injuxtaposition to the prism d. This correcting prism has its varyingpowers inversely arranged with respect to the prism 11 with the resultthat the deflected rays of light are caused to pass through the tworisms in proper relation to each other so that 51c image is reproducedon the screen without being distorted or possessing the aberration abovereferred to.

It is, of course, obvious that if the prism d v is moving'in thedirection of the arrow shown in Figure 3, the prism (1* would have to bemoved in the reverse direction as shown by its arrow.

In view of the difliculties encountered in mechanically operatingstraight prisms, I

. prefer to revolve said prisms, but this operation brings in anotheraberration due to the curvature of the prisms which curvature must becompensated for and corrected, otherwise a distortion and vibration ofthe image on the screen would result.

As shown in Figure 4, the prism (Z is curved about its axis of movementas its center while the prism d" has an opposite curvature about itsaxis of movement as a center, the two 0perative portions of prisms d andd" overlapping, with the result that the lenticular for mation of thetwo opposing curved surfaces willcorrect or neutralize-the aberrationwhich otherwise would be produced by the curvature of one prism.

the apparatus shown in Figure '1, the

prism d is mounted on a wheel 18 secured to I shaft 1, While the prism Jis mounted on the wheel 19 secured to shaft 13, the prisms thus beingcaused to move in opposite directions at their point of intersection. 7

While I prefer to revolve both the prisms-d and d 'as above I may insome casesrevolve only one of them placing such of the opposingcorrections as are d sirable on the other which would then remainstationary. V

The wheels 18 and 19 carrythe prisms d and 11" respectively, and, asshown in Figure 6, and

to correct the aberration'of the prism a 1,c99,aaa

for purposes ofexplaining my present invention, 'I will assume thatthese prisms are spi ral in form as well as varied in strength. The

end d of prisms d is of low power while the end (i is ofhigh power,whereas with respect to the 'prism d on wheel 19 the end cl is of lowower, while the endd is of high power.

In t is manner, as the wheels 18 and 19 rotate in the direction of theirarrows, the picture, when it is first brought into view, will beprojected by the low power portions of the prisms and superposed incorrect registration upon the image passing from view with the resultthat the lowermost picture passes from view and the overlapping ends ofthe prisms are rotated so thatbut one picture will be projected onto thescreen and the image held stationary by the moving prisms whose angularpowers so deflect the rays of light as to hold the image on the screenstationary, notwithstanding the fact that the film containing thepicture is moving. a 4

In operation, assuming that the first picture on the film is going intoview, the revolution of the wheels 18 and 19 will pick up said firstpicture, first with the low power prisms, and as said picture descendsthe changing angularity of the prisms will hold the image stationary onthe screen until extinguished by any suitable dissolver or shutter. Itwill be seen that at no time in the exposure of a film is hght entirelycut oil from the screen, but on the contrary, the same strength of lightis at all time maintained upon the screen, except method of correctingaberrations is well I I known to those skilled in the art as applicablein a moderate amount of correction, but for very fine corrections, theapochromatic system may be employed.

The cross sections of the prisms d and cl" clearly show such astructure, they being composed of two prisms of opposite angles one ofwhich would ordinarily be crown and the other flint glass.

In order to use prisms of moderate powers and, strength, it is highlydesirable that the prisms should be as far as possible away from thepicture, but in doing this itgets the prisms so far away from thepictures as to require objective lenses of long focal length; but longfocal length lenses will project'images that are so small as to beimpracticable. To overcomethis difiiculty, introduce a negative lenssystem 20, that is.

lenses of negative power in front of the ob lens system of asymmetricalfocal lengths in a manner very similar to that used in the telephotosystem of lenses.

To insure re 'ster and focus of the images on the screen, it is obviousthat any suitable means can be employed, many of which are well known,to adjust the lenses and the prisms relative to each other, or to thefilm, and it is immaterial whether this adjustment with respect to thefilm involves a movement of the film, or of the prisms or the lenssystem. x

In order to avoid travel ghosts, that is variations of light on thescreen, I arrange a prism 21 (see Figure 1), between the source of lightand the film, whereby the rays of light are ke t uniformly centered onthe portion of the film being exposed. This prism 21 is preferablyconcentric in form and varies in strength proportionate to the. movementof the film.

My invention also contemplates using reflecting mirrors which ma be inthe form of spirals completely encirc ing the wheel or sections of spirasabove referred to, this system being illustrated in Figure 5 wherein tere is shown, diagrammatically, a contemplated arrangement whereinspiral reflecting mirrors are employed, and in this figure I havedesignated the source of light as a, condensing lenses as b, the pictureto be pro-.

jected as-c, the objective lens or system of lenses as e, and the imagethrown on the screen as a: is the first mirror of the system, and y, thesecond mirror. The mirror m is arranged in spiral form in a mannersimilar to the prisms d, heretofore described, and it is obvious thatthe aberration resulting from curvature of the mirror a: will becorrected b an o posite curvature of the mirror y. ne of t ese mirrorsa; or y is mounted on the exterior ofa wheel and'is thereby given apositive curvature, whereas the other mirror is mounted on the interiorso as to have an opposite or negative curvature to correct the positivecurvature of the first mentioned mirror.

It is obvious that instead of having a single spiral either in the prismarrangement or the arrangement of the mirrors wherein said prisms ormirrors overlap their spiral ends slightly to temporarily expose twopictures at the same time, the aperture in the k plate 25 could be madeof such size as to ac coinmodate two or more pictures at once,

and the spiral prism or mirror continued to make a double spiral or aspiral of two or more turns, whereby two or more images may be pro ectedon the screen continuously. Tlns construction and the construct on ofthe single spiral above referred to is, of course, applicable for use inconnection with color transparencies commonly employed in conjunctionwith the well known colored picture projecting machine. These colorscreens would be arranged preferabl in spiral form in a similar mannerto the de ectors diagrammatically shown in Figure 1-,*the differentcolors being separated from each other for reasons which are obvious. Ihave indicated these color screens as 2 in Figure 1. lVhcrc two or morecolor transparencies are em-- ployed they would have to be separatefronr -i each other, either in the form of two or more spirals commonlyknown as a multiple spiral,

there being a transparency of a different color in front of differentpictures.

lVhile I have shown my apparatus as operating continuously, that is,that the pictures are moved past the aperture in the plate 25non-intermittently, it is obvious that if desired, an intermittent feedcould be employed, in' which event the prisms would be in action duringthe feed movement of the film, but when the film is stationary theprisms could either remain stationary, or

.their power could be made uniform, or said prisms could be cut awayentirely. This same operation would obtain with respect to the mirrorconstruction shown in Figure In using the word picture or film in theaccompanying claims, it will be understood that these words or either ofthem mean either a film transparency with a picture thereon, or anopaque sheet or strip as paper with a picture thereon, printed matter,diagrams, charts, etc.

"When the term deflect is employed, it is to be understood as meaningdeflection produced by surfaces which will deflect, retract ordifi'ract, or other means of deviating a ray of light.

It will be seen that during the revolution of the wheels 18 and 19 thereis a moment when two pictures are simultaneously projected inregistryupon the screen, this of course would produce a flashing 'orchange in illumination during this overlap. In order to avoid thisflashing some means of dissolving the light must be provided such as theconventional finger dissolver commonly used in dissolving stereopticons.Such a dissolver is conventionally shown in Figure 1, at 22. By tl-c useof this dissolver the total illumination is kept uniform during thetransition period.

Having now described my invention I wish to claim Claims:

1. In an apparatus of the character described, the combination withmeans for feeding a picture strip and a source of light, of a system oflenses. a movable spiral prism of varying strength, in optical alignmentwith the picture on the strip that is to be exhibited and the lenses,and means for synchronizing the movement of the picture-strip and theprism.

2. In an apparatus of the character described, the combination withmeans for feeding a picture strip and a source of light, of

- 3. The combination stated in claim 2 when the movable prisms are ofspiral formation;

4. In an apparatus of the character described,'the combination withmeans for feedsystem of lenses,

images are to be powers, which register a ing a picture strip and asource of light towhich the picture strip is exposed, of a systemoflenses, a movable spiral prism of varied strength, and meansfordissolving the images projected from the strip, the said 'prism anddissolving means being in optical alignment with the picture to beexhibited and the lenses, and means for synchronizing the movements ofthe picture strip, the prism and the dissolving means.

5. In an apparatus of thecharacter de-- scribed, the combination withmeans forfeeding a picture strip and a source of light to which thepicture'strip is exposed, of a system of lenses, a plurality of movable,op-

positely arranged spiral prisms of -varied strength, means fordissolving the images projected from the strip,

with the picture tobe exhibited and the lenses, and means forsynchronizing the movements of the picture strip, the prisms and thedissolving. means.

6. In an apparatus of the character described, the combination withmeans for feeding a picture strip and a source of light, of a a movableprism of varied strength, means for projecting the image of the oncomingpicture with gradually increasing intensity and for simultaneously andgradually extinguishing the image of the outgoing picture, and means forsynchronizing the movements of the picture strip, the dissolving meansand the prism.

In an apparatus of the character described, the combination with meansfor feed ing a plurality of movable pictures whose projected, of asystem of plurality 'of movable prisms of strength and differentrefractive plurality of images on a screen and hold them stationaryduring the movement of said pictures, and means for admitting 'andshutting ofl" rays of light to and from the pictures the said-severalmoving parts having their movements synchronized with reference to eachother.

-8. In an apparatus of the character delenses, a varied scribed. thecombination with a holder for a the screen for locating the image of thepicture upon the screen, a second, correcting, PIlSIIl, of differentrefractive power arranged the prisms and dis-- solving means belng 1noptical al gnment 7 neeaaae to receive the light from the first prismand transmit it to the screen so as to correct chromatic aberrations,and means for synchronizing the movements of the picture and the said.twoprisms. v V j t 9. In an apparatus of the character de scribed, thecombination with a holderfor a movable picture whose image is to-beprojected onto a screen and a source of light, of a system of lenses, amovable spiral prism are ranged between the picture and the screen forlocating the image of the picture upon .the screen, a second prism ofdifl'erent refrac- -movements of t epicture and the said two ing tolocate the image of the picture upon the screen, and means forsynchronizing the movements of the picture and the prism.

11. In combination, means for feeding a picture strip having a pluralityof pictures thereon to be projected upon a screen, a source of light anda system of lenses for projecting images of the pictures upon thescreen, means operated in synchronism with the strip feeding mechanismfor maintaining the images stationary upon the screen while thecorresponding pictures pass the projecting system, and means forprojecting the image of the oncoming picture upon the screen withgradually increasing intensity and for simultaneously and graduallyextinguishing the image of the outgoing icture. 1

12. In com ination, means for feeding a no picture strip havinga'plurality of pictures thereon to be projected upon a screen, a sourceof light and a system of lenses for projecting images of the pictures,upon the screen, means operated in synchronism with the strip feedingmechanism for'maintaining the images stationary upon the screen whilethe corresponding pictures pass the projecting system,- comprising aspiral prism having varying strength throughout its len h and ha goverlapping ends, whereby the images of both the oncoming and theoutgoing pictures are simultaneously projected .upon the screen whilethe overlapping ends of the prism pass the projecting system.

13. In-combination, means-for feeding a picture strip having a pluralityof pictures thereon to be projected upon a screen, a source of light anda system of lenses for projecting images of the pictures upon thescreen, 130

rotating the prism in the path of the images in synchronism With thestrip feeding mechaupon the screen 'Whiie the corresponding ictures passthe projecting system, and light tering means associated with theoverlapping ends of the' prism for simultaneously 0 gradually increasingthe intensity of the image of the oncoming picture and decreasing theintensity of the outgoing picture.

ed m 1919.

In testimony whereof I have hereunto afnism for maintaining the imagesstationary fix y signature this 2nd day of December, 15

PENROSE E. CHAPMAN.

